1. Field of the Invention
The present invention relates to a liquid crystal display device and a method for manufacturing the liquid crystal display device.
2. Description of the Related Art
In recent years, display devices (flat panel display) which are very thin and lightweight as compared to cathode-ray tube display devices have developed. The flat panel displays include liquid crystal display devices which have liquid crystal elements, electro-luminescent (EL) display devices which have self-light emitting elements such as EL elements, plasma displays, and the like, and they are in competition in the market.
Although each kind of flat panel display has good points and bad points as of now, the liquid crystal display devices are inferior to the other flat panel displays in the response time of an element (the speed of switching the display). Various techniques for overcoming the disadvantage in the response time have been proposed so far. A conventional liquid crystal element which employs a driving method of a liquid crystal called a twisted nematic (TN) mode has a response time of approximately 10 milliseconds, whereas a liquid crystal element which employs an optical compensated birefringence (OCB) mode or a ferroelectric liquid crystal (FLC) mode has realized an improved response time of approximately 1 millisecond (see Patent Document 1, for example).
Another technique which attracts as much attention as such a driving method of a liquid crystal uses a state called a blue phase for a liquid crystal display element. The blue phase is a liquid crystal phase which appears between a chiral nematic phase having a relatively short spiral pitch and an isotropic phase, and has a feature of an extremely short response time. The liquid crystal display element using a liquid crystal layer which exhibits the blue phase does not need to have an orientation film and can widen a viewing angle and thus is expected to be put into practical use. However, the blue phase is exhibited in a small temperature range of 1° C. to 3° C. between a cholesteric phase and an isotropic phase. Thus, there is a problem in that the temperature of the element needs to be controlled precisely.
In order to solve this problem, it is proposed that the temperature range of the blue phase be widened by polymer stabilization treatment (see Patent Document 2, for example). The polymer stabilization treatment is performed in such a manner that a photocurable resin is mixed into a liquid crystal material and light irradiation is performed at a temperature at which the blue phase is exhibited.